1. Field of the Invention
The present invention is generally in the field of electrical circuits. More specifically, the invention is in the field of high-frequency switching circuits.
2. Related Art
High-frequency switching devices, such as high-frequency switching devices having multiple inputs and a shared output, can be used in mobile communication devices, such as cellular handsets, to provide operation at more than one frequency. For example, a high-frequency switching device can be used in a cellular handset operating in a system using a global system for mobile communications (GSM) communications standard to enable the cellular handset to operate either at a low band frequency of 900.0 MHz or a high band frequency of 1800.0 MHz by selectively coupling a corresponding input to the shared output. For high-frequency switching devices, such as high-frequency switching devices used in mobile communication devices using the GSM communications standard, there is a continuing need to provide high power handling capability and low harmonic output, such as low third harmonic output.
A conventional high-frequency switching device can include two or more switching blocks, where each switching block includes a number of field effect transistors (FETs) coupled together, and where each switching block is coupled to a separate input and a shared output. The gates of the FETs in each switching block can be coupled to a control voltage input, which can provide a high control voltage to turn on the switching block and a low control voltage to turn off the switching block. To achieve increased power handling capability, the number of FETs in each switching block can be increased. However, increasing the number of FETs in each switching block undesirably increases the semiconductor die area consumed by the switching device. To reduce harmonic output, a first capacitor can be coupled between the gate and drain of the FET in each switching block that is coupled to the shared output of the switching device and a second capacitor can be coupled between the gate and source of the FET in each switching block that is coupled to an input of the switching device. However, this solution does not provide a sufficient reduction in harmonic output for many applications.
Thus, there is a need in the art for a high-frequency switching device that provides increased power handling capability and reduced harmonic output.